Using Old Oyster Shells As Substrate For Juveniles, UNH Oyster Restoration Efforts Come Full Circle
By Rebecca Zeiber, NH Sea Grant
September 5, 2007
Lab superviser Jenn Greene holds a Great Bay oyster shell that is being
used as the substrate for tiny oyster "spat" to grow on for
the UNH oyster shell recycling program and oyster reef restoration efforts
in the bay. Photo, Rebecca Zeiber.
Ray Grizzle wades slowly in the shallow waters at the mouth of the Bellamy
River, inspecting the river bottom and finding some shells.
“2006 was a good year, maybe the best ever,” he says thoughtfully,
in much the same manner a wine connoisseur would talk about a fine vintage
red. Instead, Grizzle is speaking about the 2006 “spat,” or
young oysters, around the Great Bay Estuary, one that added numerous
juvenile oysters to the depleted population.
Grizzle, UNH research professor of zoology, and research technician
Krystin Ward have spent the morning loading up a boat with bins containing
oyster shells dotted with one million oyster spat, each no larger than
a grain of sand. After a short trip out to the Bellamy at low tide, Grizzle
stops the boat and they begin gently tossing the shells into the water
near tall PVC pipes marking the location of their continued oyster reef
“People ask, ‘why oysters? What’s the big deal?’” Grizzle
says. “Well, some consider them to be a keystone species: they
filter the water column for their food, they provide habitat and food
for other species, including humans, and in northern estuaries, they
are a unique species, one that’s important ecologically.”
The concept of oyster reef restoration isn’t new, but in Great
Bay some changes have taken place to make this particular one unique.
In previous years, the oysters were raised for a few months at UNH’s
Jackson Estuarine Laboratory (JEL) prior to their release into the restoration
This made the job more difficult and time consuming, as the baby oysters
were required to grow in size, making the bins heavier. In addition,
they would often attach themselves to one another or to the sides of
the bins. When the shells were separated to place individuals in the
restoration site, it was a call to action for the species that feed on
“The sound made by the shells when we broke them apart was like
ringing the dinner bell for oyster predators,” says Jenn Greene,
lab supervisor. “You would see this army of mud snails moving across
the mud flat, just swarming around the oysters. Some oysters will be
consumed, that’s just a fact of life out there.” Although
the mud snails are not usually considered predators, they do feed on
dead and dying oysters.
Placing the juvenile oysters in the restoration site when they are mere
specks on a shell could prove to be a quicker and more cost-effective
method of restoration if the set is successful. In addition, Grizzle
explains that oyster spat of that size (less than one millimeter) won’t
have the scent associated with them that larger, broken oysters do and
therefore may not attract as many predators, thus allowing survival to
“Since we started the restoration program in 1999, it has really
evolved,” Grizzle says. “One of the major conclusions we
have drawn is that we need more hard substrate for baby oysters to grow,
and the best substrate is old oyster shells.”
But the bigger story, at least for those working at Grizzle’s
lab, is where those old oyster shells have originated.
“Oysters are harvested from the bay, eaten, and the shells are
thrown into the landfill,” Grizzle says. “That’s not
the natural cycle. We wanted to complete the cycle that this species
should be going through naturally by putting shells back into the estuary.” So
with the help of Greene, the UNH Oyster Shell Recycling Program was developed
The Bellamy River restoration site that Grizzle and Ward are working
on is the completion of that cycle, thanks to this recycling program.
All the shells they are placing in the Bellamy are from Great Bay and
have been donated by the public, including recreational oyster harvesters.
A trailer located near JEL allows locals to drop off their used shells
into separate large plastic bins for use in the recycling and restoration
The idea behind a shell recycling program is similar in nature to those
in southern states, including South Carolina, but on a much smaller scale.
Grizzle approached Ken La Valley, extension agent for NH Sea Grant, for
help in writing a grant to get the program started locally.
“This project is an ideal example of community helping science,” La
Valley says. “They had a need for shell to enhance their restoration
efforts, as well as the funding necessary to devote their time. We paired
them up with Cooperative Extension and NH Sea Grant to get money, and
we came up with a way to make it work.”
Getting the program off the ground also required the development of
a hazardous analysis and critical control point (HACCP) plan. La Valley
explains that these plans are normally used in the seafood, restaurant
and processing industries as a preventative program that identifies potential
hazards in a manufacturing process of food handling situations. These
hazards often include pathogens that put consumers at risk. In the case
of the shell recycling program, developing a HACCP plan allowed researchers
and managers to minimize the risk of bringing pathogens or exotic species
into the bay.
Along with UNH, the N.H. Fish and Game Department encourages the public
to return oyster shells once they’ve eaten the meat. Bruce Smith,
marine biologist with the department’s Marine Fisheries Division,
says that they sell between 400-600 oyster harvesting licenses per year,
and each license holder is sent a letter recommending they return the
shells once they’ve eaten the meat.
The department is in charge of keeping track of and setting the harvesting
regulations, such as the number of oysters harvested and tools used.
Although recreational harvest is allowed in certain locations, other
oyster beds are not open for such activity due to pollution loads from
nearby wastewater treatment facilities, Smith explains. A portion of
the Bellamy River oyster reef restoration project is one of those locations,
thus providing a sanctuary for a possible rebound in the oyster population.
Although the oyster reef restoration efforts have resulted in both successes
and failures over the years, the shell recycling program has added a
positive component to the overall project goals.
“I believe we’re beginning to see a change in something
that will become important ecologically and societally,” Grizzle
says. “I see some glimmer of hope for the oysters coming back in
For more information about this research, contact Jenn Greene at 2-1244.